User Contributed Notes 2 notes

If we omit using a filter then PHP by default puts a filter which is FILTER_DEFAULT which will use default filter. Now the question is what is a default filter. A default filter is unsafe_raw which will allow the unsafe raw data passed on to the server. This value is available in php.ini file. It is suggested that a developer should update this value inside php.ini file as under:filter.default = full_special_charsfilter.default_flags = 0

Whereas in php.ini file above values are by default, set as under:;filter.default = unsafe_raw;filter.default_flags =

Above semicolons are commented out lines so surely one needs to remove those semicolons to apply the changes made. If we do not do above things then what will happen. In that case PHP will use default filter which would surely be FILTER_UNSAFE_RAW and one can see that unsafe raw data can then be passed onto server which can make the life a hacker easier.

While it may seem to be good practice to set the defaults in php.ini you should not assume that the end users server has the same settings as your server. Because of this you should not presume that default filtering will work out of the box for the end user.

You should ensure that all filters are declared at the site of use regardless of your own default settings. A move to a new host even for your own personal application may break due to different settings.